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Re: Sandwich Panels

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edean(--nospam--at) wrote:
> Does anyone have information/comments on the applicability
> and use of insulated sanwich panels as part of a roof
> structure.  The panels would be used to construct the roof
> deck and would span 8ft between manufactured joists.
> These are an engineered proprietary system, basically
> consisting of rigid insulation sandwiched between two
> sheets of plywood creating a 6in or 8in thick section.
> There is no other lumber within the panel section. The
> rigid insulation is glued to the plywood and acts
> compositely.  I believe the panels are 4ft wide and can be
> made in lengths up to 20ft or so.  Diaphragm capacity
> would be provided by 2x lumber blocking at the panel
> edges, between sheets,allowing the panels to be connected
> together.
> I believe this system has seen significant use in
> residential construction in some markets, but we are being
> asked by the contractor to consider it as
> value-engineering alternative to a panelized wood roof
> system for a commercial application.  Some particular
> concerns are:
> Longterm performance.
> Degradation of the insulation/plywood adhesive bond.
> Creep.
> Diaphragm Capacity.
> Ductility.
> Shrinkage of the perimeter panel lumber.
> Thanks in advance for any comments.
> Ed DeanI can't remember the name of the panel (I believe it was called 
Insulspan) but I plan checked a project that proposed to use the panels 
for walls as well as roof's. The only real problem that I had with the 
panels was:
1. No approved ICBO report or COLA report for use in Los Angeles. 
Certifications that I reviewed were for wind loading normal to the panel 
and for gravity loads only. The panels had not been tested for shear or 
for story drift. 
2. The company provided analysis from an engineer in Wisconsin, but 
could was not willing to cover the cost for proper testing. 

We ended up not approving the system. The other problems had to do with 
shear transfer through the diaphram where the connection (a long lag 
screw - proprietary) was subjected to bending. The standard details 
provided really didn't address lateral design.

Hope this helps somewhat.
Dennis Wish PE